1. Field of the Invention
The present invention relates to an image forming apparatus capable of receiving, through an interface, a signal line, etc., image data corresponding to a character or an image, transmitted from a host apparatus such as a personal computer, and capable of forming an image on printing medium such as paper or a thin plastic plate based on the received image data.
In particular, the present invention relates to an image forming apparatus adapted to be connected to a network and to be used in common by plural host apparatuses.
2. Related Background Art
As for an image forming apparatus (hereinafter also called printing apparatus) for printing on a printing medium a text or the like prepared in a computer or a word processor, laser beam printer (LBP) and ink jet printer have recently replaced the conventional dot matrix printer and have become popular.
At present, there are already commercialized an LBP capable of representing gradations in high quality with a high resolution, and an ink jet printer capable of representing not only a color image of business purpose with 8 to 16 colors but also a full color image of photographic quality.
On the other hand, in order to fully exploit the printing performance of such high-performance printers, there are commercialized various high-quality printing media such as glossy paper, coated paper, glossy film, etc.
There is also commercialized a high-quality multi-functional printer capable of preparing various on-demand prints by storing sheets of plural kinds or sizes and by being provided with plural printing heads.
Also, with respect to print data (hereinafter also called image data) to be printed by such printers, it becomes possible to easily create not only the print data of conventional monochromatic text but also those containing color graphics or natural photographs by merely utilizing an ordinary word processing application software functioning on a personal computer (PC), owing to the recent rapid progress in the PC technology, whereby there is being realized an environment for handily producing high-quality on-demand prints. Also, with respect to the printer driver software for processing the print data prepared by such application software so as to match the printer or for transferring the print data to such printer, there is already commercialized a software capable of automatically analyzing the print data and automatically selecting appropriate print medium and print mode for each page.
Such on-demand prints are prepared particularly in the office environment. With the rapid spreading of the network environment in recent years, the PC is not used independently in the office but plural PC's are connected to a network in order to share various data and information. In such environment, the printer is not directly connected to the individual PC but is connected as a printer server to the network and is shared by the plural client PC's.
However, in case of preparing the on-demand prints in the office environment or the like by transferring the print data to the high-quality multi-functional printer connected to the network through the aforementioned printer driver software capable of automatically selecting the print medium and the print mode, if a printing operation cannot be continued because the print medium of the selected kind is not available or is exhausted in the course of the printing operation or because the print head to be used in the selected print mode is not loaded in the printing apparatus, the printing apparatus is continuously in the waiting state. As a result, unless a user who has instructed the printing operation executes a print canceling process for canceling the printing operation, other users are unable to use such printer.
Such locked state of the printer can be released by providing the printer driver software with a function of forcedly executing a print canceling process in case the waiting state of the printer continues for a predetermined period. In such configuration, however, the print output is forcedly canceled in the course of the printing operation. For example, when after a printing operation for 100 sheets is started, the entire printing operation is canceled merely because a color photographic image incidentally contained in only one sheet in the early part of the printing operation cannot be properly printed, the printer has to be considered less convenient for use by the automation of the printing apparatus.